Multiple-channel conduit with separate wall elements

ABSTRACT

A multiple channel tube and method of making such a tube. The preferred method includes providing a plurality of wall elements that are elongated in a longitudinal direction and that that have an elongated cross-section transversely to the longitudinal direction. The wall elements have opposite lateral sides disposed on opposite ends of an elongate axis of the cross-section. The wall elements are placed between first and second sheet members, and the opposite lateral sides of the wall elements are adhered to the sheet members to provide a plurality of channels defined between the adhered wall elements and the sheet members.

FIELD OF THE INVENTION

The present invention relates to a multiple-channel conduit and a methodof making such a conduit, such as a heat exchanger tube. Moreparticularly, the present invention relates to a heat exchanger in whichwall elements are adhered to a sheet to define channels.

BACKGROUND OF THE INVENTION

Heat exchanger tubes have traditionally been constructed by soldering orbrazing crests of an undulating spacer sheet within a flattened tube, asdescribed, for instance in U.S. Pat. No. 4,998,580. Discrete, hydraulicflow-paths are thus provided between the undulations of the spacer. Thisstructure improves the heat conduction between the outside of theflattened tube and the fluid flowing therethrough.

U.S. Pat. No. 4,360,958 teaches another method of making a heatexchanger, in which a plurality of passageways are provided by insertingwires into a flattened tubular member. The wires are spaced and disposedin parallel from each other and have surfaces with a lower melting pointthan the tubular member. The surfaces of the wires are then heated toabove their melting point to secure them to the tube.

Another teaching that uses wires is U.S. Pat. No. 2,396,522, in whichsquare cross section rods or circular cross-section wires that arewelded to walls. Depending on the materials used, the parts can besoldered or welded together. The side edges of the assemblies taughthave angular features.

A new heat exchanger construction is needed that can simplifyconstruction and reduce required material, and preferably allow use ofhigh internal pressure. The present invention now provides a solution tothis need.

SUMMARY OF THE INVENTION

The present invention is directed to a new multiple-channel conduit,such as a tube for use in heat exchange applications, and to a method ofproducing such a conduit. In the preferred embodiment, a plurality ofwall elements are provided. The wall elements are preferably elongatedin a longitudinal direction and have an elongated cross-section orientedtransversely to the longitudinal direction. The wall elements also haveopposite lateral sides that are disposed on opposite ends of an elongateaxis of the cross-section. The wall elements are placed between firstand second sheet members, and opposite sides of the wall elements areadhered to the sheet members to define a plurality of channels betweenthe adhered wall elements and sheet members.

Preferably, the wall elements are adhered to the sheet members bymelting a material, such as by melting the wall element or sheetmaterial in a welding process, or by melting a separate material, suchas in a brazing or soldering process. Most preferably, the oppositelateral sides of the wall elements are welded to the sheet members byapplying an electrical current therebetween in an amount sufficient tomelt a portion of the material of each sheet member. The preferred typeof welding to be used is electrical-resistance welding.

The wall elements are preferably made by compressing and flattening oneor more wires, such as by roll forming. A welding projection can beprovided extending laterally at the opposite lateral sides of the wallelements in a configuration to promote welding to the sheet members.

The sheet members themselves can be part of the single sheet or canalternatively be made from separate sheets. This sheet can be bentaround an interior space within which the wall elements are adhered tothe sheet members. The lateral ends of the sheet are preferably adheredto each other such as by welding to enclose and define at least one ofthe channels in cooperation with at least one of the wall elements. Thebent and adhered sheets preferably forms an exterior flattened tube.

The wall elements preferably have a lateral width measured between theirlateral sides of less than about 10 mm, more preferably less than about5 mm, and most preferably less than about 2 mm. At least one of thesheet members and/or wall elements has a thickness of less than about0.5 mm. The wall elements and sheet members can be made of any suitablematerial, and a preferred material is copper, a copper alloy or steel.

The preferred tube is formed to provide a heat exchanger tube. In thepreferred heat exchanger tube, the plurality of wall elements arepreferably of separate construction from each other, but are connectedby the sheet that surrounds the wall elements and to which they areadhered. Welds, or alternatively brazing or soldering joints, preferablyadhere the wall elements to the sheet. In one embodiment, the tubeextends along a serpentine pattern.

The invention thus provides an improved structure and the method ofmanufacturing for a multiple-channel tube, the production of which canbe easily scalable and not prone to wasting significant amounts ofmaterial.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective cross-sectional view of a wire used to form awall element of a preferred embodiment of the invention;

FIG. 2 is a perspective cross-sectional view of the wire formed as awall element;

FIG. 3 is a cross-sectional view of a lateral end of a wall element incontact with a sheet member for adhesion thereto;

FIG. 4 is a perspective cross-sectional view of a heat exchanger tubeconstructed according to the preferred embodiment of the invention;

FIG. 5 is a perspective cross-sectional view showing wall elements beingadhered to a sheet in the production of a heat exchanger tube;

FIG. 6 is a perspective cutaway view of a plurality of heat exchangertubes associated with a header;

FIG. 7 is a front view of a heat exchanger that includes a plurality ofheaders and associated heat exchanger tubes;

FIG. 8 is a side cross-sectional view of another embodiment of a heatexchanger;

FIGS. 9-11 are end views of alternative embodiments of tubes constructedaccording to the invention;

FIG. 12 is a cross-sectional view of a lateral end of an alternativeembodiment of a wall element with a sheet member for adhesion thereto;and

FIG. 13 is a front view of an embodiment of a heat exchanger with aserpentine tube.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIG. 1, a plurality of wires 10 are preferably flattened,such as by rolling or other compression process, to form wall elements12, as shown in FIG. 2. The wall elements 12 are preferably elongated ina longitudinal direction 14, typically corresponding to the axialdirection of the wire 10. Additionally, the wall elements 12 preferablyhave a cross-section that is elongated transversely with respect to thelongitudinal direction, in a lateral direction 16, with opposite lateralsides 18 disposed on opposite ends of an elongate lateral axis of thecross-section. The cross-section is preferably the cross-section of theentire wall element 12, but can alternatively be of a wall portionthereof that extends substantially between sheet portions that define atube. The wall elements 12 are preferably of separate construction andcan be positioned independently in a tube to be produced.

The wall elements 12 are preferably further prepared for a subsequentwelding process. As shown in FIG. 3, the lateral sides 18 of the wallelements 12 are formed with a welding projection, which can include anub 20 that runs longitudinally and projects laterally. The nub 20 isconfigured promote welding of the lateral wall element sides 18.Projection welding techniques, as known in the art can be employed atthe lateral sides, which improve the quality of electrical-resistancewelded joints in high-conductivity alloys because they concentrate thewelding current where desired.

In the preferred embodiment, the wall elements 12 are adhered to anouter sheet 22 that surrounds the wall elements 12 to form an exteriortube 24, as shown in FIG. 4, which preferably has a flattened, ovalprofile. The adhered wall elements 12 divide the interior of theexterior tube 24 into a plurality of channels 26 through which a liquidcan be flowed in an assembled heat exchanger.

The sheet defines two sheet portions or members 28,30. Preferably sheetmember 28 is joined with one set of lateral sides 18 of the wallelement, and sheet member 30 is joined with the set of lateral sides 18on the opposite lateral side. Although the sheet members 28,30 are partof a unitary single sheet in the preferred embodiment, in an alternativeembodiment, the exterior tube can be formed from one or more sheets thatare joined together. In one embodiment, the first and second sheetmembers are joined together from separate sheet stock.

The wall elements 12 are preferably adhered to the sheet 22 by welding,although other processes can alternatively be employed, such as brazingor soldering. Preferably, electrical-resistance welding is used. Thewall elements 12 can be welded to the sheet 22 sequentially orsimultaneously.

Additionally, the wall elements 12 can first be welded to one of thesheet members 28 when the sheet 22 is in an open configuration shown inFIG. 5. The sheet 22 can then be folded around the adhered wall elements12, and the wall elements 12 can be welded the other sheet member 30 ina subsequent operation. Most preferably, however, the wall elements 12are adhered to both opposing sheet members 28,30 in a single operation,such as by using electrode rollers in opposite sides of the ovalexterior tube 24.

The free edges 32 of the sheet members 28,30 are preferably sealed toeach other, such as by welding, preferably electrical-resistance weldingor high-frequency welding, or by another suitable process, such asbrazing or soldering. The weld can be a high frequency weld to form aseal between the welded members. If the free edges 22 are to be welded,one or both of these can be formed with welding protrusions, for examplewith a configuration similar to the protrusions 20 shown in FIG. 3. Inthe assembled heat-exchanger tube 44 shown in FIG. 4, welds 34 arepresent between the wall members 12 and the sheet 22 and between thewelded sheet edges 32, with the wall elements 12 forming walls dividingthe channels 26 in the interior space of the tube 24. One of thechannels 26 is sealed by the weld 34 between the sheet members 28,30. Inan alternative embodiment, the free ends 32 can be disposed in anotherlocation along the exterior tube, including extending through one of thesheet members 28,30 or on one of the flat sides of the exterior tube.

While other methods of adhering the wall elements 12 to the sheet 22 canbe used, the preferred methods involve melting a material to effect thejoining or fusing. While welding is preferred, most preferably thewelding is accomplished by applying an electrical current between theportions to be welded. The preferred welds are seam welds, which can bemade with wheel or roller electrodes, as known in the art. The seamwelds 34 that are produced preferably seal the channels 26 from eachother and from the exterior of the tube 24. Overlapping weld locationscan be produced to provide a substantially continuous weld line.

The wall elements 12 and sheet 22 can be formed of the same material. Ina preferred embodiment, a thin, high strength, brass material is usedfor the sheet 22, such as SM2385, and copper or a copper alloy is usedfor the wall elements 12, such as C12200. Aluminum, steel, their alloys,and other metals are other suitable materials. While materials with goodheat conductivity are preferably used, in certain embodiments, such asin which heat exchanging properties are not critical, other materialscan be employed, including plastics. Different welding and adhesionmethods can be used to adhere plastic parts.

The preferred lateral width 36 of the adhered wall elements 12 is lessthan about 10 mm, more preferably less than about 5 mm, and mostpreferably less than about 2 mm or 1.5 mm. A preferred embodiment has alateral width 36 of around 1 mm. Preferably, the lateral width 36 is atleast about 0.3 mm, and more preferably at least about 0.4 or 0.6 mm.The thicknesses 38 of the sheet 22 and the wall elements 12 arepreferably less than about 0.5 mm, more preferably less than about 0.3mm, and most preferably less than about 2 mm. A typical thickness 38 isaround 0.15 mm, and is preferably at least about 0.05 mm, and morepreferably at least about 0.1 mm.

The inventive heat exchanger tubes are preferably assembled in aradiator or other heat exchanger, such as in a refrigerant condenser orevaporator, oil cooler, a charge-air cooler or other heat exchangedevice. The tubes can be used in cooling or heating applications, inwhich heat is conducted into or out from the cooling fluid that flowsthrough the channels 26.

The number and locations of the wall elements 12 in the tube 24 can bevaried and selected to provide channels 26 of different or the samesizes as each other. The lateral widths 36 of the wall elements 12 canalso be varied as well. While the preferred embodiment has an elongatedcross-section tube 24 with substantially flat side walls 42, othershapes can be obtained. Similarly, while the wall elements 12 arepreferably substantially straight and have generally smooth andrelatively flat surfaces, other curved configurations can also be used.The spacing between the wall numbers 12 can be decreased to withstandhigher internal pressures, or increased to reduce production cost whenatmospheric or low internal pressures are used in the assembled heatexchanger.

The invention thus provides a low cost manufacturing process that can bescalable, such as by increasing or reducing the number of wall elements12. In particular, if high speed welding is used to join the wallelements and sheet members, substantially no additional or wastedmaterial is needed or produced to manufacture the tubes in the preferredembodiment. To facilitate attaching and sealing, such as by brazing,soldering, or welding, in the subsequent assembly of an inventive heatexchanger tube in a radiator or other heat exchanger structure, as shownin FIG. 6, a smooth exterior surface can be provided on the outside ofthe assembled heat-exchanger tube, preferably without sharp bends.

In the embodiment of FIG. 6, a plurality of tubes 44 are brazed to around tube header 46. The tubes 44 are inserted into elongated slots 48in the curved sidewall of the header 46 and brazed or otherwise adheredthereto. The exterior surface of the tubes 44 are thus preferablysubstantially smooth, preferably rounded, and preferably alsosubstantially free of small concavities, nooks, or other features thatwould hinder extensive sealing around the exterior thereof where thetubes 4 meet the header 46. Thus, any seams, such as between the ends 32of the sheet members 28,30, are substantially smooth, so as to reduce oreliminate gaps in the seal between the tubes 44 and the header 46. Theseseals 50 and the wall elements 12 that are fixed to the sheet members28,30 better allow the flow of refrigerant under pressure if desired.The seals 50 thus preferably can withstand elevated internal pressuresas used in pressure flow heat exchangers, and the wall elements 12preferably resist or prevent outward bowing of the sheet members 28,30due to the pressurized refrigerant flowing through the tubes 44.Preferably, the tubes 44 can withstand at least about 500 psi, and morepreferably at least about 600 psi. A preferred embodiment uses coolantat about 650 psi. By placing the wall elements 12 closer together, forinstance, an embodiment can withstand internal coolant pressures ofabove about 1500 psi or 2000 psi.

Although the header 46 shown is generally cylindrical, other shapes canalso be employed, such as headers with a D-shaped cross-section.Additionally, serpentine fins 48 can be joined to the tubes 44, and arepreferably joined with pairs of adjacent tubes 44, in thermal conducingassociation therewith to improve heat exchange with the medium flowingover the exterior of the heat exchanger.

FIG. 7 shows an assembled heat exchanger 52 with a plurality of tubes 44affixed in fluid association with headers 46 to provide a four-passflat-tube condenser or evaporator. The fins 48 can be placed near thelongitudinal ends of the tubes 44 or substantially along the tubes 44entire longitudinal length. An extra set of fins 48 can be associatedwith the tubes 44 at the lateral sides of the heat exchanger and can beadditionally supported by members, such as support tubes or plates 100which can be provided without a fluid so much as to the header 46 orother prism carrying the refrigerant. The headers are divided internallyby walls 54 to direct the refrigerant flowing therethrough in aplurality of passes, such as the four passes provided in the embodimentshown. Sequentially, a first pass is made between the headers 46 throughtubes 56, a second pass is made through tubes 58, a third pass is madethrough tubes 60, and a fourth pass is made through tubes 62. Therefrigerant is fed into header 46 before the first pass through inlettube 64, and the refrigerant is outlet from the header 46 after thefourth pass through outlet tube 66. The inlet and outlet tubes are alsoadhered to the header 46, preferably be welding, and alternatively bebrazing or soldering or another suitable method.

As shown in FIG. 8, an alternative embodiment of a header 68 isD-shaped, and formed of a curved portion 70 and is fixed and sealed by asuitable method of adhesion, including welding, brazing, and soldering,to a U-shaped member 72. The tubes 44 have two wall elements 12 with alongitudinal length 74 that is shorter than the longitudinal length 76of the sheet members, preferably with longitudinal portions 78 at thelongitudinal ends of the tubes 44 free of the wall elements 12.

FIGS. 9-11 show alternative constructions of the inventive tubes. Thetube 80 of FIG. 9 has wall elements 12 positioned at the front and backends of the tube 80. These wall elements 12 thus can be exposed at thefront and back sides, and preferably seal the outer channels 82. Sheetmembers 84 are substantially flat. Tube 86 of FIG. 10 has sheet members88 of separate construction that are welded or otherwise adhered andsealed at both front and back sides, at which the opposing sheet members88 are preferably curved to form the outermost channels 90. Theembodiment 92 of FIG. 11 has one flat sheet member 94 that is welded orotherwise adhered and sealed to a sheet member 96 with lateral sheetends, which will become the front and back sides of the tube, that arecurved to join the flat sheet member 94.

The preferred elongated cross-section of the wall elements, generallytaken obliquely to the longitudinal direction, has an aspect ratio of atleast about 1.2 of lateral length, in direction 16 corresponding to thefront to back axis of the assembled tube, to shorter width, in direction98 corresponding to the front to back axis of the assembled tube, asshown in FIG. 2. More preferably, the aspect ratio is at least about1.5, and most preferably at least about 1.75. Certain embodiments canhave a much higher aspect ratio, such as shown in FIG. 4, of above about5 or more.

The aspect ratio of the tube cross-section itself is preferably greaterthan about 2, more preferably greater than about 5, and most preferablygreater than about 10, and preferably less than about 30, and morepreferably than about 20. The cross-section and the tube major and minordiameters are preferably measured on the outside of the tube 44.

Referring to FIG. 13, an embodiment of a heat exchanger 102 includes atube 44 that is bent in a serpentine manner, with bends 104 andpreferably straight portions 108. Fins 106 are in thermal conductiveassociation with the serpentine portions of the tube 44. The serpentineportions 108 and 104 can be made from a single tube 44, or a series oftubes. The radius 110 of the bends 104 is preferably less than about 3times the size of the tube cross-section that is parallel to the radius,which is preferably the small cross-sectional diameter of the tube 44,measured along the minor axis of the tube cross-section. In oneembodiment, the bend 104 has a radius that is about 2.8 times thecross-sectional diameter parallel therewith, which is preferably theminor or major diameter of the cross-section. Another embodiment has aradius that is up to about 4 times and more preferably up to about fiveof 10 times the cross-sectional width parallel to the radius. In oneembodiment, the fin height or tube pitch 112 between the preferablygenerally parallel tube portions 108 is between about 8 and 9 mm; thetube cross-section small diameter is between about 1 mm and 2 mm, andmore preferably about 1.3 mm; the tube cross-section large diameter isbetween about 10 mm and 20 mm, and most preferably around 16 mm; and thebend radius 110 is from about 3 mm to about 4 mm, more preferably toabout 8 mm or 10 m, and in one embodiment is about 4.9 mm, and inanother is about 3.75 mm.

The bend portions can be made without wall segments, but preferablyinclude the wall segments. Other constructions of wall segments or otherinternal supports for the pressure-supporting tube walls or otherinternal channel dividers can alternatively be used. The preferredmaterial is copper or a copper alloy for tubes 44 of heat exchanger 102,although other suitable materials may be used.

While illustrative embodiments of the invention are disclosed herein, itwill be appreciated that numerous modifications and other embodimentsmay be devised by those skilled in the art. For example, weldingprojections or other structures to promote welding can additionally beprovided on the sheet to improve welding to the wall elements. Thesewelding projections on the sheet can be used in conjunction with orinstead of, the welding projections on the lateral sides of the wallelements. Additionally, certain embodiments of the wall elements can bemade without welding projections, such as shown in FIG. 12. Althoughsome embodiments use sealed wall elements to prevent the flow across thetube internal channels, others permit such flow. Therefore, it will beunderstood that the appended claims are intended to cover all suchmodifications and embodiments that come within the spirit and scope ofthe present invention.

1. A method of producing a multiple-channel conduit, comprising:providing a plurality of wall elements that are elongated in alongitudinal direction and that have an elongated cross-sectiontransversely to the longitudinal direction, the wall elements havingopposite lateral sides disposed on opposite ends of an elongate axis ofthe cross-section; and adhering the opposite lateral sides of the wallelements to first and second sheet members such that the wall elementsare disposed therebetween and defines a plurality of channels betweenthe adhered wall elements and sheet members.
 2. The method of claim 1,wherein the elongated cross-section has an aspect ration of at leastabout 1.2.
 3. The method of claim 1, wherein the elongated cross-sectionhas an aspect ratio of at least about 1.5.
 4. The method of claim 1,further comprising melting a material to adhere the opposite lateralsides to the sheet members.
 5. The method of claim 4, wherein theopposite lateral sides are adhered to the sheet members by welding,brazing, or soldering.
 6. The method of claim 4, wherein the oppositelateral sides are welded to the sheet members by applying an electricalcurrent therebetween in an amount sufficient to melt a portion of thematerial of each sheet members.
 7. The method of claim 6, wherein theopposite lateral sides are electrical-resistance welded to the sheetmembers.
 8. The method of claim 1, further comprising compressing wireto form the wall elements.
 9. The method of claim 8, wherein the wire iscompressed by roll forming.
 10. The method of claim 1, wherein theplurality of wall elements are formed with a welding projectionextending laterally at the opposite lateral sides and configured promotewelding to the sheet members.
 11. The method of claim 1, wherein thesheet members are part of a single sheet.
 12. The method of claim 11,further comprising bending the sheet around an interior space, whereinthe wall elements are adhered to the sheet members within the interiorspace.
 13. The method of claim 12, further comprising adhering lateralends of the single sheet to enclose and define one of the channels. 14.The method of claim 1, wherein the wall elements have a lateral widthbetween the lateral sides of less than about 10 mm.
 15. The method ofclaim 14, wherein at least one of the sheet members has a sheetthickness of less than about 0.5 mm.
 16. The method of claim 1, whereinthe wall elements and sheet members are made of copper or a copperalloy.
 17. The method of claim 1, wherein the conduit is formed toprovide a heat exchanger.
 18. The method of claim 1, wherein theexterior of the sheet members adhered to the wall elements issubstantially smooth to facilitate sealing to a header.
 19. The methodof claim 1, further comprising bending at least a portion of theassembled conduit with the wall elements disposed at least along bentportion.
 20. A multiple channel heat exchanger, comprising: a pluralityof wall elements that are separate from each other and are elongated ina longitudinal direction and that that have an elongated cross-sectiontransversely to the longitudinal direction, the wall elements havingopposite lateral sides disposed on opposite ends of an elongate axis ofthe cross-section; and a sheet surrounding the wall elements; whereinthe opposite lateral sides of the wall elements are adhered to the sheetto provide a plurality of channels defined between the adhered wallelements and the sheet members.
 21. The heat exchanger of claim 20,further comprising a weld adhering the lateral sides of the wallelements to the sheet.
 22. The heat exchanger of claim 20, furthercomprising a brazing or solder joint adhering the wall elements to thesheet.
 23. The heat exchanger of claim 20, wherein the wall elementshave a lateral width between the lateral sides of less than about 10 mm.24. The heat exchanger of claim 20, wherein the wall elements have alateral width between the lateral sides of less than about 5 mm.
 25. Amultiple-channel conduit, comprising a tube that comprises comprising: across-section with a major and a minor diameter; bend portions that arebent about a radius with a parallel dimension of the cross-section beingparallel to said radius; and channel partitions that define channelswithin the tube, wherein the partitions are provided in the bendportions
 26. The conduit of claim 25, wherein the radius is less thanabout 10 times the parallel dimension, and the conduit is configuredalong a serpentine pattern.